The invention relates to a method for controlling a pressure fluid operated percussion device which allows a tool movable in its longitudinal direction with respect to a body of the percussion device to be installed therein, and which comprises a working chamber and therein a transmission piston installed movably in the axial direction of the tool in order to suddenly compress the tool in its longitudinal direction by a pressure of pressure fluid influencing the transmission piston such that a stress pulse is generated in the tool in its longitudinal direction and the stress pulse progresses through the tool into a material to be broken, a control valve which includes inlet and discharge channels for conveying pressure fluid to and from the percussion device and which also includes a movably installed switch element provided with channels for switching, via the channels of the switch element, the inlet channels and, similarly, the discharge channels to alternately feed pressure fluid into the working chamber to influence the transmission piston and, similarly, to discharge pressure fluid that influenced the transmission piston from the working chamber.
The invention further relates to a percussion device which allows a tool to be installed therein movably in its longitudinal direction with respect to a body of the percussion device, and which comprises a working chamber and therein a transmission piston installed movably in the axial direction of the tool in order to suddenly compress the tool in its longitudinal direction by a pressure of pressure fluid influencing the transmission piston such that a stress pulse is generated in the tool in its longitudinal direction and the stress pulse progresses through the tool into a material to be broken, a control valve which includes inlet and discharge channels for conveying pressure fluid to and from the percussion device and which also includes a movably installed switch element provided with channels for switching, by means of the switch element and via the channels thereof, the channels to alternately convey pressure fluid into the working chamber to influence the transmission piston and, similarly, to discharge pressure fluid that influenced the transmission piston from the working chamber.
In the claimed percussion device, a stress pulse is generated such that a transmission piston residing in a separate working chamber is arranged to be influenced by the pressure of pressure fluid, most preferably relatively suddenly. The influence of the pressure pushes the transmission piston towards a tool. Consequently, the tool becomes compressed, whereby a stress pulse is generated in the tool and the stress pulse progresses therethrough, and when the tip of the tool is in contact with rock or another hard material to be broken, makes the material break down. In order to control its striking operation, the percussion device may utilize a rotatable or reciprocally linearly movable switch element which typically comprises successive openings to ultimately open a connection from a pressure fluid source to the transmission piston of the percussion device and, similarly, from the transmission piston to a pressure fluid reservoir. When drilling conditions change, or for some other reasons, it is sometimes desirable to change the frequency at which stress pulses are generated, which is easy to carry out by adjusting the speed of movement of the switch element. However, a problem arises in that when the speed of movement of the switch element increases, the times during which pressure fluid channels are open become shorter. This contributes to changing the operation and behaviour of the device, which is not desirable.